This invention relates generally to fluid dispensing apparatus, and, in particular, to multiple fluid mixing and dispensing apparatus.
Prior art devices used to pump two or more fluids to a mixing head where the fluids are sprayed onto a surface or injected into a cavity are relatively common.
Some devices utilize independently driven fluid pumps in which the driving means is regulated to obtain a predetermined ratio of fluid volume flow and in which the pressure and temperature of the separate fluids are also monitored to assure a uniformity of result.
Other devices utilize various differing methods of obtaining a predetermined ratio of fluid volume being pumped. Some devices achieve this result by varying the orifice size of a venturi to vary the suction rate at which the fluids are withdrawn from their reservoirs. Other devices utilize piston and gear arrangements in the mixing head for metering the flow of fluid.
Still other devices use several pumping cylinders of different volumes linked by an actuator arm to simultaneously pump fluids at a predetermined mix ratio.
Other devices use positive displacement pumps having a fixed volume ratio, however, an adjustable length actuating arm is used to vary the ratio of stroke length, and therefore volume, when simultaneously pumping from their respective fluid reservoirs.